making session variable active on dynamically created subdomains - php

Question

I was working on a web project which allows users to create their own sub domains dynamically.
Before creating a subdomain they should be logged in to the website.
And now was wondering how to set session variable of a user active even on the subdomains which he visits.
Tried with lot of functions like
session_set_cookie_params(0, '/', '.example.com');
**ini_set('session.cookie_domain', '.example.com' );**
but all in no wain. No function works .
So please do suggest me how to handle this.
here is my code which starts the session as soon as the user log's in:
checkusrlog.php
<?php
//for session to be active on subdomain
session_set_cookie_params(0, '/', '.xyz.com');
session_start(); // Start Session First Thing
error_reporting(E_ALL);
ini_set('display_errors', '1');
include_once "connectiontomysql.php"; // Connect to the database
$dyn_www = $_SERVER['HTTP_HOST'];
//------ CHECK IF THE USER IS LOGGED IN OR NOT AND GIVE APPROPRIATE OUTPUT -------
$logOptions = ''; // Initialize the logOptions variable that gets printed to the page
$newMessage = '';
// If the session variable and cookie variable are not set this code runs
if (!isset($_SESSION['idx'])) {
if (!isset($_COOKIE['idCookie'])) {
$logOptions = 'Register Account
|
Log In';
}
}
// If session ID is set for logged in user without cookies remember me feature set
if (isset($_SESSION['idx'])) {
$decryptedID = base64_decode($_SESSION['idx']);
$id_array = explode("p3h9xfn8sq03hs2234", $decryptedID);
$logOptions_id = $id_array[1];
} else if (isset($_COOKIE['idCookie'])) {// If id cookie is set, but no session ID is set yet, we set it below and update stuff
$decryptedID = base64_decode($_COOKIE['idCookie']);
$id_array = explode("nm2c0c4y3dn3727553", $decryptedID);
$userID = $id_array[1];
$userPass = $_COOKIE['passCookie'];
// Get their user first name to set into session var
$sql_uname = mysql_query("SELECT username, email FROM siteMembers WHERE id='$userID' AND password='$userPass' LIMIT 1");
$numRows = mysql_num_rows($sql_uname);
if ($numRows == 0) {
// Kill their cookies and send them back to homepage if they have cookie set but are not a member any longer
setcookie("idCookie", '', time()-42000, '/');
setcookie("passCookie", '', time()-42000, '/');
header("location: index.php"); // << makes the script send them to any page we set
exit();
}
while($row = mysql_fetch_array($sql_uname)){
$username = $row["username"];
$useremail = $row["email"];
}
$_SESSION['id'] = $userID; // now add the value we need to the session variable
$_SESSION['idx'] = base64_encode("g4p3h9xfn8sq03hs2234$userID");
$_SESSION['username'] = $username;
$_SESSION['useremail'] = $useremail;
$_SESSION['userpass'] = $userPass;
$logOptions_id = $userID;
?>
Note: all subdomains are managed with only single piece of code where the data which belogs to that particular subdomain is dump from database dynamically based on the subdomain.
In between am working on a shared hosting service and using *.streamicon.com as Root domain. Using *.streamicon.com as my root domain as it allows me to create 'n' number of subdomains dynamically.